The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

Bob Hewitt jailed for rape, sexual assault

South Africa's Supreme Court has rejected an appeal by former grand slam tennis champion Bob Hewitt, ruling that he must serve a six-year jail sentence after being convicted of the rape and sexual assault of young girls he coached decades ago.

A panel of three judges at the Supreme Court of Appeal said in a judgment released Thursday that the prison sentence given to Hewitt was appropriate.

Hewitt, now 76, was convicted of the offences in 2015.

He was found guilty of raping two girls and sexually assaulting a third in the 1980s and 1990s.

The Australia-born, naturalised South African Hewitt, won 15 grand glam titles in doubles and mixed doubles, most notably partnering Fred Stolle to two Wimbledon and two Australian Open mens doubles titles.

He also won the 1979 French Open mixed doubles with Australia's Wendy Turnbull, nine years after he first lifted that trophy alongside the legendary Billie Jean King.

He has been held under a form of house arrest at his farm in southern South Africa since his conviction.